Stack molds are used for high volume production, in which rows of mold cores and mold cavities are stacked in a single machine. In conventional stack molds, a central, first mold plate is provided, typically for holding the mold cavities of the respective stacks of molds. Typically, the central plate comprises two or more abutting plates, and connects with cooling lines and the like.
Two outer, second mold plates typically hold the respective mold cores, with the entire system opening and closing during the molding process. One of the outer, second mold plates is typically affixed to a stationary platen of a conventional molding machine, while the other outer mold plate is attached to the moveable platen, so that one of the outer, second mold plates and the central first mold plate move in the opening and closing process of molding.
In prior art systems, leader pins are provided which interengage between the mold plates, to laterally align them while the stack mold is in the closed, molding position, but are separated in the open position. Also, in conventional stack molds, an external rack and pinion system is provided to keep the central, first mold plate properly spaced between the outer, second mold plates at all times.
In an improvement on the conventional stack molds, the M-U-M-S modular unit mold system base is made by the Plas-Tool Company of Niles, Illinois. The "hot runner plate", which is the first, central mold plate, has outrigger supports that rests on tiebars to support its weight, the movement of the mold being horizontal.
Unfortunately, the exposed rack-and-pinion system, and other external moving parts, have created a risk for accident and injury among mold operators. Also, debris such as plastic fragments can jam into exposed threads of a rack and pinion system or the like, disabling the molding machine. There is a need for a reliable mold system in which parts such as a rack and pinion or other threaded systems are not exposed, reducing the risk for accidental entanglement with the user or for jamming of the threaded system.
Another system for spacing the central first plate (also called the floating hot runner assembly) comprises a threaded rod carried by one plate, which engages a threaded sleeve carried by another plate, this being manufactured by the Hasco Company of Germany. These are attached to the peripheries of the respective mold plates, and serve to keep the first, central mold plate centered. However, the moving threads of the rods also represent the potential for a serious accident, if clothing of a user of the mold becomes entangled in the rotating rod during mold operation. They also may become jammed with debris.
By this invention, a mold, and preferably a stack mold, is provided, having an increase in efficiency and safety of operation, with the spacing and support structures being more protected so that there is a great decrease in the likelihood of entanglement of a user's clothing, resulting in serious injury to the mold operator or other bystander as the mold closes. Also, the chances for jamming of the mold with debris are reduced.